Despite having just begun the 2014 cycle, we have already seen more Senate retirements than we did in all of 2000, 2002, 2006 and 2008.

Note: Number of retirements in 2014 includes just the first two months of the election cycle. (Data courtesy of Roll Call Casualty List.)

And if just four more senators opt for retirement this cycle -- which is very possible -- the number of retirements over the last three election cycles will be the highest in four decades.

Currently, 24 senators have called it quits between 2010 and today -- just three less than the previous high of 27 retirements between 1992 and 1996.

The most likely additional retirees would seem to be Sens. Tim Johnson (D-S.D.), Carl Levin (D-Mich.), Thad Cochran (R-Miss.), Mike Enzi (R-Wyo.) and Jim Inhofe (R-Okla.). And as with Johanns, there are always a few surprise retirements along the way.